Base station and apparatus

ABSTRACT

A base station according to an embodiment comprises: a controller including a memory. The controller is configured to store a list in the memory, the list including at least one or more identifiers of Wireless Local Area Network (WLAN) access points. The controller is further configured to execute a process of receiving first information from a node configured to connect to the WLAN access points. The first information includes at least one ore more identifiers of WLAN access points to be deleted from the list. The controller is further configured to update the list on a basis of the first information.

RELATED APPLICATIONS

This application is a continuation application of internationalapplication PCT/JP2015/081211, filed Nov. 5, 2015, which claims benefitof JP Patent Application 2014-227440, filed Nov. 7, 2014, the entiretyof all applications hereby expressly incorporated by reference.

TECHNICAL FIELD

The present application relates to a base station and a wireless LANaccess point, used in a system in which a switching process of switchinga standby target or a connection target between a coverage area of amobile communication network and a coverage area of a wireless LAN isexecuted.

BACKGROUND ART

Conventionally, there is proposed a switching process (a networkselection and a traffic steering) of switching, by a radio terminal, astandby target or a connection target between a mobile communicationnetwork and a wireless LAN when a coverage area of the mobilecommunication network represented by LTE (Long Term Evolution) and acoverage area of the wireless LAN overlap at least partially (see NonPatent Literature 1, for example).

Specifically, the switching process is executed on the basis of theradio terminal determining whether or not first information at a mobilecommunication network side satisfies a first condition, and the radioterminal determining whether or not second information at a wireless LANside satisfies a second condition. The first information and the secondinformation (hereinafter, a “determination parameter”) used by the radioterminal for determination of the switching process are notified fromthe base station arranged in the mobile communication network to theradio terminal.

It is noted that the base station notifies the radio terminal of a listof AP identifiers (hereinafter, “AP list”) indicating a wireless LANaccess point that is a candidate standby target or connection target.The radio terminal selects, on the basis of the AP list notified fromthe base station, the wireless LAN access point of the standby target orthe connection target.

PRIOR ART DOCUMENT Non-Patent Document

Non Patent Document 1: 3GPP Technical Specification “TS 36.304 V12.2.0”Sep. 23, 2014

SUMMARY

A base station according to an embodiment comprises: a controllerincluding a memory. The controller is configured to store a list in thememory, the list including at least one or more identifiers of WirelessLocal Area Network (WLAN) access points. The controller is furtherconfigured to execute a process of receiving first information from anode configured to connect to the WLAN access points. The firstinformation includes at least one or more identifiers of WLAN accesspoints to be deleted from the list. The controller is further configuredto update the list on a basis of the first information.

An apparatus for a base station according to an embodiment comprises: aprocessor and a memory. The processor is configured to cause the basestation to store a list in the memory, the list including at least oneor more identifiers of Wireless Local Area Network (WLAN) access points,and receive first information from a node configured to connect to theWLAN access points. The first information includes at least one or moreidentifiers of WLAN access points to be deleted from the list. Theprocessor is further configured to cause the base station to update thelist on a basis of the first information.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a communication system 1 according to eachembodiment.

FIG. 2 is a block diagram showing a radio terminal 10 according to eachembodiment.

FIG. 3 is a block diagram showing a radio base station 100 according toeach embodiment.

FIG. 4 is a block diagram showing an access point 200 according to eachembodiment.

FIG. 5 is an explanatory diagram for describing an operation accordingto a first embodiment.

FIG. 6 is an explanatory diagram for describing an operation accordingto a second embodiment.

DESCRIPTION OF EMBODIMENTS

[Overview of Embodiment]

A base station according to an embodiment comprises: a controllerincluding a memory. The controller is configured to store a list in thememory, the list including at least one or more identifiers of WirelessLocal Area Network (WLAN) access points. The controller is furtherconfigured to execute a process of receiving first information from anode configured to connect to the WLAN access points. The firstinformation includes at least one or more identifiers of WLAN accesspoints to be deleted from the list. The controller is further configuredto update the list on a basis of the first information.

The controller may be configured to execute a process of transmitting alist based on the updated list.

The controller may be configured to execute a process of sending aresponse to the first information, to the node.

The controller may be configured to execute a process of sending aresponse to the first information to the node if the controller refusesupdating based on the first information. The response indicates that thecontroller refuses the updating based on the first information.

The controller may be configured to execute a process of receivingsecond information. The second information may include at least one ormore identifiers of a WLAN access points to be added to the list.

An apparatus for a base station according to an embodiment comprises: aprocessor and a memory. The processor is configured to cause the basestation to store a list in the memory, the list including at least oneor more identifiers of Wireless Local Area Network (WLAN) access points,and receive first information from a node configured to connect to theWLAN access points. The first information includes at least one or moreidentifiers of WLAN access points to be deleted from the list. Theprocessor is further configured to cause the base station to update thelist on a basis of the first information.

A radio terminal that performs standby or connection in a mobilecommunication network autonomously executes a determination forswitching to a wireless LAN on the basis of a determination parameter,without receiving a direct instruction from a base station. Thus, evenwhen a base station or a wireless LAN access point does not wish theswitching process to the wireless LAN, the radio terminal may send aconnection request to a wireless LAN access point in an AP listaccording to the determination.

In this case, due to a refusal of the connection request by the wirelessLAN access point, the connection request by the radio terminal may bewasted and the switching process from the wireless LAN to the mobilecommunication network may occur immediately.

A base station according to a first embodiment (and another embodiment)is a base station configured to constitute a mobile communicationnetwork. The base station comprises: a transmitter configured totransmit first information to a radio terminal controlled by the basestation itself, the first information including one or more identifiersindicating a wireless LAN access point that is a candidate of a standbytarget or a connection target when a radio terminal switches the standbytarget or the connection target from the mobile communication network toa wireless LAN; and a receiver configured to receive a removal requestfor removing at least one or more predetermined identifiers from thefirst information, from the wireless LAN access point or a nodeconfigured to control the wireless LAN access point.

In the first embodiment, the removal request includes the predeterminedidentifiers.

The base station according to the first embodiment further comprises: acontroller configured to remove, in response to the removal request, thepredetermined identifiers from the first information.

In the first embodiment, the controller controls to transmit, when notremoving the predetermined identifiers from the first information, aresponse with an indication that the predetermined identifiers are notremoved, to the wireless LAN access point or the node from which theremoval request is transmitted.

In the first embodiment, the transmitter transmits the first informationin which the predetermined identifiers are removed, to a radio terminalsubordinated to the base station itself.

In the first embodiment, the removal request includes informationindicating a reason for removing the predetermined identifiers from thefirst information.

A wireless LAN access point according to the first embodiment comprises:a transmitter configured to transmit a removal request for removing anidentifier of the wireless LAN access point itself from firstinformation, to a base station configured to transmit the firstinformation to a radio terminal controlled by the base station itself,the first information including an identifier indicating a wireless LANaccess point that is a candidate of a standby target or a connectiontarget when a radio terminal switches the standby target or theconnection target from a mobile communication network to a wireless LAN.

A base station according to a second embodiment is a base stationconfigured to constitute a mobile communication network. The basestation comprises: a receiver configured to receive a request for aconnection determination transmitted from a wireless LAN access point inresponse to a connection request from a radio terminal to the wirelessLAN access point; and a transmitter configured to transmit a response tothe request for the connection determination, to the wireless LAN accesspoint. The response to the request for the connection determinationincludes information indicating a connection refusal reason when thebase station refuses the connection, by the radio terminal, to thewireless LAN access point.

In the second embodiment, the request for the connection determinationincludes at least any one of: information on a throughput of thewireless LAN access point; information on a load of the wireless LANaccess point; and information on a transmission stop time of thewireless LAN access point.

In the second embodiment, the connection refusal reason indicates that acause thereof is at least any one of: load balancing; the wireless LANaccess point planning to stop a transmission; a handover procedure ofthe radio terminal being executed; and a throughput of the wireless LANaccess point being not sufficient.

In the second embodiment, the transmitter transmits, to the wireless LANaccess point, either one of information designating a radio terminal forwhich the request for the connection determination is necessary, orinformation designating a time period in which the request for theconnection determination is necessary.

A wireless LAN access point according to the second embodiment is awireless LAN access point configured to constitute a wireless LAN. Thewireless LAN access point comprises: a receiver configured to receive aconnection request from a radio terminal; and a transmitter configuredto transmit a response to the connection request to the radio terminalwhen refusing the connection request, the response including informationindicating a refusal reason. The refusal reason is based on a connectionrefusal reason received from a base station configured to manage a cellin which the radio terminal exists.

The wireless LAN access point according to the second embodiment furthercomprises: a controller configured to control, when receiving theconnection request, to request, to the base station, a connectiondetermination to the wireless LAN access point. The connection refusalreason from the base station is included in a response to the requestfor the connection determination.

In the second embodiment, the refusal reason indicates that a causethereof is at least any one of: load balancing; a handover procedure ofthe radio terminal being executed; and the wireless LAN access pointplanning to stop a transmission; and a throughput of the wireless LANaccess point being not sufficient.

In the second embodiment, the refusal reason is identical to theconnection refusal reason received from the base station.

First Embodiment

(Communication System)

A communication system according to a first embodiment will bedescribed, below. FIG. 1 is a diagram showing a communication system 1according to the first embodiment.

As shown in FIG. 1, the communication system 1 includes a radio basestation 100 and an access point 200. Further, the communication system 1includes a radio terminal 10 capable of connecting to the radio basestation 100 or the access point 200.

The radio terminal 10 is a terminal such as a cell phone or a tabletcomputer. The radio terminal 10 has a function of performing radiocommunication with the access point 200, in addition to a function ofperforming radio communication with the radio base station 100.

The radio base station 100 has a first coverage area 100A, and in thefirst coverage area 100A, provides a mobile communication servicerepresented by LTE (Long Term Evolution). The radio base station 100manages one or a plurality of cells, and the first coverage area 100A isconfigured by one or a plurality of cells. The radio base station 100 isan entity of a mobile communication network. It is noted that a cell maybe thought of as a term to indicate a geographical area, and may also bethought of as a function of performing radio communication with theradio terminal 10.

The access point 200 has a second coverage area 200A, and in the secondcoverage area 200A, provides a wireless LAN service. The access point200 is an entity of a wireless LAN. At least a part of the secondcoverage area 200A overlaps the first coverage area 100A. A whole of thesecond coverage area 200A may overlap the first coverage area 100A.Generally, the second coverage area 200A is smaller than the firstcoverage area 100A.

(Application Scene) In the first embodiment, a method of performing, bythe radio terminal, the switching process (for example, a networkselection and a traffic steering) of switching a standby target or aconnection target between a mobile communication network and a wirelessLAN, will be described. The radio terminal 10 in an RRC connected stateor an RRC idle state performs a switching process in order to select anetwork in which data (packet) is exchanged, out of a mobilecommunication network (cellular communication network) and a wirelessLAN (WLAN communication network). Specifically, when a state iscontinued over a predetermined period where first information at amobile communication network side satisfies a first condition and secondinformation at a wireless LAN side satisfies a second condition, theswitching process (for example, a network selection and a trafficsteering) is executed.

In the first embodiment, the switching process includes both of: aprocess of switching a standby target or a connection target from amobile communication network to a wireless LAN, and a process ofswitching a standby target or a connection target from the wireless LANto the mobile communication network.

Here, the first information at the mobile communication network side isa measurement result (RSRPmeas) of a signal level of a received signal(RSRP: Reference Signal Received Power) and a measurement result(RSRQmeas) of a signal quality of a received signal (RSRQ: ReferenceSignal Received Quality), for example.

The second information at the wireless LAN side is a channel utilizationvalue of a wireless LAN (ChannelUtilizationWLAN), a backhaul value of adownlink of a wireless LAN (BackhaulRateDIWLAN), a backhaul value of anuplink of a wireless LAN (BackhaulRateUIWLAN), and a signal level of areceived signal (RSSI: Received Signal Strength Indicator), for example.

(Switching process from Mobile Communication Network to Wireless LAN)

A first condition that the standby target or the connection target isswitched from the mobile communication network to the wireless LAN isthat either one of the following condition (1a) or (1b) is satisfied,for example. It is noted that the first condition may be that all of thefollowing conditions (1a) to (1b) are satisfied.

(1a) RSRPmeas<Thresh_(ServingOffloadWLAN, LowP)

(1b) RSRQmeas<Thresh_(ServingOffloadWLAN, LowQ)

It is noted that “Thresh_(ServingOffloadWLAN, LowP)” and“Thresh_(ServingoffloadWLAN, LowQ)” are threshold values provided fromthe radio base station 100 or previously determined threshold values.

A second condition that the standby target or the connection target isswitched from the mobile communication network to the wireless LAN isthat all of the following conditions (1c) to (1f) are satisfied, forexample. It is noted that the second condition may be that any one ofthe following conditions (1c) to (1f) is satisfied.

(1c) ChannelUtilizationWLAN<Thresh_(ChUtilWLAN, Low)

(1d) BackhaulRateD1WLAN>Thresh_(BackhRateDLWLAN, High)

(1e) BackhaulRateU1WLAN>Thresh_(BackhRateULWLAN, High)

(1f) RSSI>Thresh_(BEACONSRSSI,HIGH)

It is noted that “Thresh_(ChUtilWLAN, Low)”,“Thresh_(BackhRateDLWLAN, High)”, “Thresh_(BackhRateULWLAN, High)”, and“Thresh_(BEACONSRSS1, High)” are threshold values provided from the basestation 100 or previously determined threshold values.

(Switching Process from Wireless LAN to Mobile Communication Network)

A first condition that the standby target or the connection target isswitched from the wireless LAN to the mobile communication network isthat the following conditions (2a) and (2b) are satisfied, for example.It is noted that the first condition may be that either one of thefollowing condition (2a) or

(2b) is satisfied.

(2a) RSRPmeas>Thresh_(ServingOffloadWLAN, HighP)

(2b) RSRQmeas>Thresh_(ServingOffloadWLAN, HighQ)

It is noted that “Thresh_(ServingOffloadWLAN, HighP)” and“Thresh_(ServingOffloadWLAN, HighQ)” are threshold values provided fromthe base station 100 or previously determined threshold values.

A second condition that the standby target or the connection target isswitched from the wireless LAN to the mobile communication network isthat any one of the following conditions (2c) to (2f) is satisfied, forexample. It is noted that the second condition may be that all of thefollowing conditions (2c) to (2f) are satisfied.

(2c) ChannelUtilizationWLAN>Thresh_(ChUtilWLAN, High)

(2d) BackhaulRateD1WLAN<Thresh_(BackhRateDLWLAN, Low)

(2e) BackhaulRateU1WLAN<Thresh_(BackhRateULWLAN, Low)

(2f) RSSI<Thresh_(BEACONSRSSI, Low)

It is noted that “Thresh_(ChUtilWLAN, High)”,“Thresh_(BackhRateDLWLAN, Low)”, “Thresh_(BackhRateULWLAN, Low)”, and“Thresh_(BEACONSRSSI, Low)” are threshold values provided from the basestation 100 or previously determined threshold values.

It is noted that when the above-described threshold values are notprovided, the radio terminal 10 may omit to acquire (that is, receive ormeasure) information in which the threshold values are not provided.

In the first embodiment, the above-described various types of thresholdvalues are examples of a determination parameter (for example, a RANassistance parameter) for determining whether or not to perform theswitching process of switching the standby target or the connectiontarget between the mobile communication network and the wireless LAN.That is, the determination parameter includes one or more valuesselected from among “Thresh_(ServingOffloadWLAN, LowP)”,“Thresh_(ServingOffloadWLAN, LowQ)”, “Thresh_(ChUtilWLAN, Low)”,“Thresh_(BackhRateDLWLAN, High)”, “Thresh_(BackhRateULWLAN, High)”,“Thresh_(BEACONSRSSI, High)”, “Thresh_(ServingOffloadWLAN, HighP)”,“Thresh_(ServingOffloadWLAN, HighQ)”, “Thresh_(ChUtilWLAN, High)”,“Thresh_(BackhRateDLWLAN, Low)”, “Thresh_(BackhRateULWLAN, Low)”, and“Thresh_(BEACONSRSSI, Low)”.

Further, the determination parameter may include a predetermined period(TsteeringWLAN) during which a state in which the radio terminalsatisfies the first condition or the second condition should becontinued. Alternatively, when an offload process of switching, by theradio terminal, the standby target or the connection target from themobile communication network to the wireless LAN is performed, thedetermination parameter may include a below-described predeterminedperiod (T350 timer value) that the radio terminal 10 should hold.

The determination parameter includes an individual parameterindividually notified from the radio base station 100 to the radioterminal 10 and a broadcast parameter broadcast from the radio basestation 100 to the radio terminal 10. The individual parameter isincluded in an RRC message (for example, RRC Connection Reconfiguration)transmitted from the radio base station 100 to the radio terminal 10,for example. The broadcast parameter is included in an SIB (for example,WLAN-OffloadConfig-r12) broadcast from the radio base station 100, forexample. It should be noted that when receiving the individual parameterin addition to the broadcast parameter, the radio terminal 10preferentially applies the individual parameter over the broadcastparameter.

(Radio Terminal)

A radio terminal according to the first embodiment will be described,below. FIG. 2 is a block diagram showing the radio terminal 10 accordingto the first embodiment.

As shown in FIG. 2, the radio terminal 10 includes an LTE radiocommunication unit (transmitter/receiver) 11, a WLAN radio communicationunit (transmitter/receiver) 12, and a controller 13.

The LTE radio communication unit 11 has a function of performing radiocommunication with the radio base station 100, and is configured by aradio transceiver, for example. For example, the LTE radio communicationunit 11 regularly receives a reference signal from the radio basestation 100. The LTE radio communication unit 11 regularly measures asignal level of a reference signal (RSRP) and a signal quality of areference signal (RSRQ). The LTE radio communication unit 11 receives,as the determination parameter, the individual parameter and thebroadcast parameter from the radio base station 100.

The WLAN radio communication unit 12 has a function of performing radiocommunication with the access point 200, and is configured by a radiotransceiver, for example. For example, the WLAN radio communication unit12 receives a beacon or probe response from the access point 200. Thebeacon or probe response includes a BBS Load information element, thechannel utilization value of the wireless LAN (ChannelUtilizationWLAN)may be acquired from the BBS Load information element. The WLAN radiocommunication unit 12 receives a response (GAS

Response) returned from the access point 200 in response to a request(GAS (Generic Advertisement Service) Request) for the access point 200.The response (GAS Response) includes a backhaul value of a downlink of awireless LAN (BackhaulRateD1WLAN) and a backhaul value of an uplink of awireless LAN (BackhaulRateU1WLAN). Such an inquiry procedure isperformed in accordance with ANQP (Access Network Query Protocol)defined in Hotspot2.0 of WFA (Wi-Fi Alliance).

The WLAN radio communication unit 12 receives a signal from the accesspoint 200. The WLAN radio communication unit 12 measures a signal levelof the received signal (RSSI). The signal level of the received signal(RSSI) is a signal intensity of the beacon or probe response.

The controller 13 is configured by a CPU (processor), a memory, and thelike, and controls the radio terminal 10. Specifically, the controller13 controls the LTE radio communication unit 11 and the WLAN radiocommunication unit 12. Further, when a state is continued over apredetermined period where the first information at the mobilecommunication network side satisfies the first condition and the secondinformation at the wireless LAN side satisfies the second condition, thecontroller 13 executes a switching process of switching the standbytarget or the connection target between the mobile communication networkand the wireless LAN.

When executing an onload process (or a re-offload process) of switchingthe standby target or the connection target from the wireless LAN to themobile communication network after performing an offload process ofswitching the standby target or the connection target from the mobilecommunication network to the wireless LAN, the controller 13 discardsthe individual parameter.

In particular, as a principle, the controller 13 is configured to holdthe individual parameter, in a period (T350 timer value) during whichthe predetermined timer (the above-described (T350 timer)) activated bythe radio terminal 10 during transition to an idle state along with theoffload process is activated. In other words, the controller 13 isconfigured to discard the individual parameter when the predeterminedtimer expires or the predetermined timer stops.

(Radio base Station)

The radio base station according to the first embodiment will bedescribed, below. FIG. 3 is a block diagram showing the radio basestation 100 according to the first embodiment.

As shown in FIG. 3, the radio base station 100 includes an LTE radiocommunication unit (transmitter/receiver) 110, a controller 120, and anetwork interface (transmitter/receiver) 130.

The LTE radio communication unit 110 has a function of performing radiocommunication with the radio terminal 10. For example, the LTE radiocommunication unit 110 regularly transmits a reference signal to theradio terminal 10. The LTE radio communication unit 110 is configured bya radio transceiver, for example. The LTE radio communication unit 110transmits, as the determination parameter, the individual parameter andthe broadcast parameter to the radio terminal 10. As described above,the LTE radio communication unit 110 notifies the radio terminal 10, byan RRC message (for example, RRC Connection Reconfiguration), of theindividual parameter, and notifies the radio terminal 10, by an SIB (forexample, WLAN-OffloadConfig-r12), of the broadcast parameter.

The controller 120 is configured by a CPU (processor), a memory, and thelike, and controls the radio base station 100. Specifically, thecontroller 120 controls the LTE radio communication unit 110 and thenetwork interface 130. It is noted that a memory configuring thecontroller 120 may function as a storage unit, and in addition to thememory configuring the controller 120, a memory configuring the storageunit may be arranged.

The network interface 130 is connected to a neighboring base station viathe X2 interface and is connected to an MME/S-GW via an S1 interface.The network interface 130 is used in communication performed on the X2interface and communication performed on the S1 interface. Further, thenetwork interface 130 may be connected via a predetermined interface tothe access point 200. The network interface 130 is used forcommunication with the access point 200.

(Access Point)

The access point according to the first embodiment will be described,below. FIG. 4 is a block diagram showing the access point 200 accordingto the first embodiment.

As shown in FIG. 4, the access point 200 includes a WLAN radiocommunication unit (transmitter/receiver) 210, a controller 220, and anetwork interface (transmitter/receiver) 230.

The WLAN radio communication unit 210 has a function of performing radiocommunication with the radio terminal 10, and has a similar function tothe WLAN radio communication unit 12 of the radio terminal 10. It isnoted that the WLAN radio communication unit 210 receives a connectionrequest from the radio terminal 10. Further, the WLAN radiocommunication unit 210 transmits a response to the connection request,to the radio terminal 10.

The controller 220 is configured by a CPU (processor), a memory, and thelike, and controls the access point 200. Specifically, the controller220 controls the WLAN radio communication unit 210 and the networkinterface 230. It is noted that a memory configuring the controller 220may function as a storage unit, and in addition to the memoryconfiguring the controller 220, a memory configuring the storage unitmay be arranged.

The network interface 230 is connected, via a predetermined interface,to a backhaul. The network interface 230 is used for communication withthe radio base station 100. Further, the network interface 230 may bedirectly connected via a predetermined interface to the radio basestation 100.

(Determination of Switching Process)

Determination of the switching process will be described by using aprocess of switching from the mobile communication network to thewireless LAN, for example, below.

Firstly, a method of determining whether or not a state where the firstinformation satisfies the first condition is continued over apredetermined period (TsteeringWLAN) will be described. The firstinformation is a measurement result (RSRPmeas) of a signal level (RSRP)of a reference signal or a measurement result (RSRQmeas) of a signalquality (RSRQ) of a reference signal, the reference signal is receivedregularly in a short cycle, and the RSRPmeas or the RSRQmeas is measuredin a relatively short cycle. That is, the RSRPmeas or the RSRQmeas isacquired continuously in a time-axis direction.

Secondly, a method of determining whether or not a state where thesecond information satisfies the second condition is continued over apredetermined period (TsteeringWLAN) will be described. There is nofixed rule about a cycle in which the second information is acquired.That is, the second information (for example, BackhaulRateD1WLAN orBackhaulRateU1WLAN) is acquired discretely in a time-axis direction.

Operation According to First Embodiment

Next, an operation according to the first embodiment will be describedby using FIG. 5. FIG. 5 is a diagram for describing an operationaccording to the first embodiment. FIG. 5 is a similar operationenvironment to FIG. 1.

The radio terminal 10 exists in the first coverage area 100A. “Existing”means that the radio terminal 10 is in a standby state (RRC idle state)in a cell managed by the radio base station 100, or in a connected state(RRC connected state) where the radio terminal 10 is connected to a cellmanaged by the radio base station 100. The radio terminal 10 is in astandby state or in a connected state, in the mobile communicationnetwork.

The radio base station 100 transmits a list of identifiers (hereinafter,“WLANID list”) indicating the access point 200 that acts as a candidateof the standby target or the connection target in the wireless LAN, tothe radio terminal 10. The radio base station 100 transmits, by an SIB,the WLANID list to the radio terminal 10. The radio terminal 10autonomously determines, on the basis of a radio signal and adetermination parameter from the access point 200 indicated by anidentifier within the WLANID list, whether to perform the switchingprocess. The radio terminal 10 transmits, to the access point 200, aconnection request (Association request), when determining to performthe switching process from the mobile communication network to thewireless LAN (see FIG. 6).

The access point 200 transmits a response (Association response) to theconnection request, to the radio terminal 10, when receiving theconnection request from the radio terminal 10. The access point 200transmits, to the radio terminal 10, the response to the connectionrequest including either information indicating an approval of theconnection request or information indicating a refusal of the connectionrequest.

The first embodiment is a case where the switching process to thewireless LAN of the radio terminal 10 is not wished by the access point200. For example, when a load of the access point 200 is large, theaccess point 200 does not wish the connection (request) of the radioterminal 10. Further, when a processing load is large, the access point200 may not wish the connection (request) of the radio terminal 10. Theaccess point 200 may not wish the connection of the radio terminal 10when planning to stop the transmission within a predetermined time (whenthe power source is turned off within a predetermined time, forexample). Further, the access point 200 may not wish the connection ofthe radio terminal 10 when a throughput of the access point 200 is notsufficient (when not possible to provide a sufficient throughput to theradio terminal 10). Further, the access point 200 may not wish theconnection of the radio terminal 10 when the number of radio terminalsconnected to the access point 200 exceeds a threshold value.

As shown in FIG. 5, when not wishing the connection of the radioterminal 10, the access point 200 transmits, to the radio base station100, a removal request (WLANID REMOVE REQUEST). The access point 200transmits the removal request, via a direct interface or backhaul withthe radio base station 100, to the radio base station 100.

The removal request is a request to remove an identifier of at least oneor more access points 200 from the WLANID list held by the radio basestation 100. The removal request includes an identifier of apredetermined access point 200 that should be removed from the WLANIDlist. The identifier of the predetermined access point 200 includes aBSSID, and an SSID, for example. The removal request may include anetwork identifier (ESSID) in the wireless LAN.

The removal request may include information indicating a reason (Cause)to remove an identifier of the access point 200 from the WLANID list.

The removal reason includes at least one of the following reasons(causes), for example.

Load of the access point 200 is large (Over load)

Processing load of the access point 200 is large (Over processing load)

The access point 200 stops transmission within a predetermined timeperiod (Turn off plan)

The throughput of the access point 200 is not sufficient (Not availablesufficient throughput)

When the removal reason is the “Over load” or the “Over processingload”, the removal request may include information on the load of theaccess point 200. The information on the load of the access point 200 isinformation indicating the magnitude of the load, for example.Specifically, the information indicating the magnitude of the load maybe either one of High, Middle, or Low, and may be an integer value.Further, when the removal reason is the “Over load”, the informationindicating the magnitude of the load may be the same index as a Compsiteavailable capacity IE. p When the removal reason is the “Turn off plan”,the removal request may include information on a transmission stop timeof the access point 200. Specifically, the information on thetransmission stop time is information indicating a transmission stoptime or a timer showing the predetermined time period. It is noted thatwhen the access point 200 stops the transmission, the access point 200may stop the transmission by stopping the WLAN radio communication unit210, or may stop the transmission as a result of the power source of theaccess point 200 being turned off.

When the removal reason indicates the “No available sufficientthroughput”, information on the throughput of the access point 200 maybe included. The information on the throughput may be informationindicating a currently measured throughput, or may be informationindicating a throughput predicted to be achievable.

When receiving the removal request, the radio base station 100 mayremove, in response to the removal request, the identifier of the accesspoint 200 from the WLANID list. Alternatively, the radio base station100 may determine whether or not to remove the identifier of the accesspoint 200 from the WLANID list. The radio base station 100 determines,on the basis of the removal reason included in the removal request, forexample, whether or not to remove the identifier of the access point200. For example, when the information indicating the magnitude of theload is lower than a threshold value, the radio base station 100determines to not remove the identifier of the access point 200. Thethreshold value may be a threshold value variable in accordance with theload of the radio base station 100. Alternatively, when the throughputof the access point 200 is higher than the threshold value, the radiobase station 100 determines to not remove the identifier of the accesspoint 200. The threshold value may be a threshold value variable inaccordance with the QoS of the radio terminal 10 within a cell of theradio base station 100.

The radio base station 100 may transmit a response to the removalrequest, to the access point 200. When refusing the removal request,that is, when not removing the identifier of the access point 200, theradio base station 100 may transmit the response to the access point200. As a result, the access point 200 is capable of knowing from theWLANID list that the identifier of the access point 200 is not removed.

It is noted that the access point 200 may know from the WLANID listwhether or not the identifier of the access point 200 is removed, on thebasis of the WLANID list, from the radio base station 100, included inthe SIB.

The radio base station 100 is capable of transmitting, by the SIB, theWLANID list (that is, an updated WLANID list) in which the identifier ofthe access point 200 is removed, to the radio terminal 10 within thecell of the radio base station 100. The radio base station 100 maytransmit the updated WLANID list to the radio terminal 10 within thecell of the radio base station 100, triggered by the removal of theidentifier of the access point 200 from the WLANID list.

It is noted that the access point 200 in which the identifier of theaccess point 200 is removed from the WLANID list may transmit, to theradio base station 100, an addition request to add the identifier of theaccess point 200 to the WLANID list, when the cause in which the radioterminal 10 does not wish the connection is resolved (when there is noremoval reason described above). The radio base station 100 adds, inresponse to the addition request, the identifier of the access point 200to the WLANID list. Alternatively, when a predetermined time passessince removing the identifier of the access point 200, the radio basestation 100 may add the removed identifier of the access point 200 tothe WLANID list. It is noted that information (a timer, a time, and thelike) indicating the predetermined time may be included in the removalrequest sent from the access point 200.

Summary of First Embodiment

In the first embodiment, the radio base station 100 receives the removalrequest from the access point 200. As a result, the identifier of theaccess point 200 may be removed from the WLANID list transmitted fromthe radio base station 100 to the radio terminal 10. The radio terminal10 does not transmit the connection request to the access point 200removed from the WLANID list, and thus, when the access point 200 doesnot wish the switching process to the wireless LAN, it is possible todecrease the radio terminal from performing the connection request tothe access point 200.

Second Embodiment Operation According to Second Embodiment

Next, an operation according to the second embodiment will be describedby using FIG. 6. FIG. 6 is an explanatory diagram for describing anoperation according to the second embodiment. Similar portions to theabove-described first embodiment will not be described whereappropriate.

The first embodiment is a case where the switching process to thewireless LAN of the radio terminal 10 is not wished by the access point200. The second embodiment is a case where the switching process to thewireless LAN of the radio terminal 10 is not wished by the radio basestation 100.

As shown in FIG. 6, within a first coverage area 100 of a cell managedby the radio base station 100, there is the access point 200. Further,the first coverage area 100A and the second coverage area 200A of theaccess point 200 overlap at least partially. In the present embodiment,a whole of the second coverage area 200A overlaps the first coveragearea 100A.

As shown in FIG. 6, the radio terminal 10 is in the first coverage area100A, and is in the second coverage area 200A. The radio terminal 10 isin a standby state or in a connected state, in the mobile communicationnetwork. In this case, it is assumed that the radio terminal 10determines to perform the switching process from the mobilecommunication network to the wireless LAN.

In step S10, the radio terminal 10 transmits a connection request(Association request) to the access point 200 indicated by an identifierof the WLANID list.

In step S20, the access point 200 transmits a request for a connectiondetermination (RAN decision request) in response to the connectionrequest from the radio terminal 10, to the radio base station 100. Therequest for the connection determination is to request the radio basestation 100 to determine whether to approve or refuse the connection bythe radio terminal 10 to the access point 200.

The request for the connection determination includes the identifier (UEID) of the radio terminal 10. The access point 200 may include, whenreceiving a connection request from a plurality of radio terminals 10, alist of identifiers (UE IDs) of the plurality of radio terminals 10,into the request for the connection determination.

Further, the request for the connection determination includes theidentifier of the access point 200 from which the request for theconnection determination is transmitted.

The request for the connection determination may include at least anyone of: information on the throughput of the access point 200,information on the load of the access point 200, and information on thetransmission stop time of the access point 200. These information arethe same information as described in the first embodiment.

It is noted that the radio base station 100 may transmit, to the accesspoint 200, information (the identifier of the radio terminal 10, forexample) designating the radio terminal 10 that requires the request forthe connection determination, and designation information designating atime period (from 08:00 to 20:00, for example) during which the requestfor the connection determination is required. The access point 200transmits the request for the connection determination, on the basis ofthe designation information.

For example, the access point 200 transmits the request for theconnection determination, when the identifier of the radio terminal 10that transmits the connection request matches an identifier of a radioterminal 10 included in the designation information. Otherwise, theaccess point 200 does not transmit the request for the connectiondetermination. Alternatively, the access point 200 transmits the requestfor the connection determination, when within the time period includedin the designation information. Otherwise, the access point 200 does nottransmit the request for the connection determination. Alternatively,the access point 200 transmits the request for the connectiondetermination, when before the timer included in the designationinformation expires. The access point 200 does not transmit the requestfor the connection determination, when a timer included in thedesignation information expires. As a result, it is possible to preventan increase in signaling based on the transmission of the request forthe connection determination.

The radio base station 100 that receives the request for the connectiondetermination determines whether to approve or refuse the connection bythe radio terminal 10 to the access point 200. The radio base station100 determines, on the basis of the information included in the requestfor the connection determination, for example, whether to approve orrefuse the connection by the radio terminal 10 to the access point 200.For example, when the information indicating the magnitude of the loadis lower than a threshold value, the radio base station 100 determinesto approve the connection by the radio terminal 10 to the access point200. The threshold value may be a threshold value variable in accordancewith the load of the radio base station 100. Alternatively, when thethroughput of the access point 200 is higher than the threshold value,the radio base station 100 determines to approve the connection by theradio terminal 10 to the access point 200. The threshold value may be athreshold value variable in accordance with the QoS of the radioterminal 10 within a cell of the radio base station 100.

In step S30, the radio base station 100 transmits a response to therequest for the connection determination (RAN decision response) to theaccess point 200. The response to the request for the connectiondetermination includes the identifier (UE ID) of the radio terminal 10and the identifier (WLAN AP ID) of the access point 200 of thetransmission target. It is noted that when the request for theconnection determination includes a list of the identifiers of theplurality of radio terminals 10, the response to the request for theconnection determination includes the list of identifiers of theplurality of radio terminals 10.

Further, when the radio base station 100 approves the connection by theradio terminal 10 to the access point 200, the response to the requestfor the connection determination indicates a connection approval(Permit). When the radio base station 100 refuses the connection by theradio terminal 10 to the access point 200, the response to the requestfor the connection determination indicates a connection refusal (notpermit). In this case, the response to the request for the connectiondetermination includes information indicating a connection refusalreason.

The connection refusal reason includes at least any one of the followingreasons (causes), for example.

-   -   Load balancing    -   The access point 200 stops transmission within a predetermined        time period (Turn off plan)    -   Handover procedure of the radio terminal 10 is being executed        (Ongoing HO sequence)    -   The throughput of the access point 200 is not sufficient (Not        available sufficient throughput)

It is noted that in the Load balancing, the load of the access point 200may be high, and the load of the radio base station 100 may be low.

Further, in a case where the radio base station 100 controls thetransmission stop time of the access point 200 (where the access point200 does not know the transmission stop time), for example, theconnection refusal reason indicates a reason that the access point 200stops the transmission within a predetermined time period.

Further, when the handover procedure of the radio terminal 10 is beingexecuted, the reason why the connection is refused is because it isdesirable that the radio terminal 10 determines the switching process onthe basis of the determination parameter of the radio base station 100after the handover. It is noted that during a handover sequence, theradio base station 100 that acts as a source base station is capable ofsetting the determination parameter of the radio base station 100 thatacts as a target base station to the radio terminal 10.

In step S40, the access point 200 that receives the response to therequest for the connection determination transmits, to the radioterminal 10, a response (Association response) to the connection requestfrom the radio terminal 10. The access point 200 transmits, in responseto the response to the request for the connection determination, aresponse to the connection request indicating either the approval of theconnection request or the refusal of the connection request. When theresponse to the connection request indicates the refusal of theconnection request, the response to the connection request includesinformation indicating the refusal reason in a Status Code field. Therefusal reason is based on a connection refusal reason included in theresponse to the request for the connection determination. For example,the refusal reason is identical to the connection refusal reasonincluded in the response to the request for the connectiondetermination.

The refusal reason included in the response to the connection requestincludes at least any one of the following reasons (causes), forexample.

-   -   Load balancing    -   The access point 200 stops transmission within a predetermined        time period (Ready for energy saving (or Turn off plan))    -   Handover procedure of the radio terminal 10 is being executed        (Ongoing HO sequence)    -   The throughput of the access point 200 is not sufficient (Not        available sufficient throughput)

The refusal reason may be the same expression as the connection refusalreason included in the response to the request for the connectiondetermination, and may be a different reason from the connection refusalreason. Therefore, the access point 200 may change the connectionrefusal reason included in the response to the request for theconnection determination and include the changed connection refusalreason into the response to the connection request. For example, theaccess point 200 may transmit, to the radio terminal 10, the response tothe connection request including, as the refusal reason, the “Ready forenergy saving (preparation for energy saving)”, when the connectionrefusal reason from the radio base station 100 indicates the “Turn offplan”.

The radio terminal 10 that receives the response to the connectionrequest indicating the approval of the connection request starts theprocess for connecting to the access point 200.

On the other hand, the radio terminal 10 that receives the response tothe connection request indicating the refusal of the connection requestis capable of performing an operation according to the refusal reason,for example. For example, when the Load balancing is the refusal reason,the radio terminal 10 is capable of stopping transmitting the connectionrequest. When the access point 200 stopping the transmission within apredetermined time period and the throughput of the access point 200being not sufficient are the refusal reason, the radio terminal 10 iscapable of transmitting a connection request to another access point200. W the handover procedure of the radio terminal 10 is beingexecuted, the radio terminal 10 is capable of determining, after thehandover procedure is ended, the switching process on the basis of thedetermination parameter of the target base station.

Summary of Second Embodiment

In the second embodiment, the radio base station 100 receives therequest for the connection determination transmitted from the accesspoint 200 in response to the connection request, sent from the radioterminal 10, to the access point 200. The radio base station 100transmits the response to the request for the connection determination,to the access point 200. The access point 200 transmits the response tothe connection request, to the radio terminal 10. When refusing theconnection by the radio terminal 10 to the access point 200, the radiobase station 100 includes the information indicating the connectionrefusal reason, into the response to the request for the connectiondetermination. The response to the connection request includes theinformation indicating the refusal reason based on the connectionrefusal reason received from the radio base station 100. As a result,the access point 200 is capable of including the reason that the radiobase station 100 refuses the connection, into the response to theconnection request. Thus, even when the switching process to thewireless LAN is not wished by the radio base station 100, the radioterminal 10 is capable of knowing the connection refusal reason of theradio base station 100. As a result, the radio terminal 10 is capable ofdetermining whether to transmit the connection request on the basis ofthe refusal reason, and thus, it is possible to reduce an unnecessaryconnection request.

Other Embodiments

The contents of the present application are described through each ofthe above-described embodiments, but it should not be understood thatthe discussion and the drawings constituting a part of this disclosurelimit to the contents of the present application. From this disclosure,various alternative embodiments, examples, and operational technologieswill become apparent to those skilled in the art.

In each of the above-described embodiments, the access point 200exchanges the above-described signaling with the radio base station 100;however, this is not limiting. For example, an access controller (AC)configured to control the access point(s) 200 may transmit and receivethe above-described signaling with the radio base station 100. Forexample, in the first embodiment, the AC, instead of the plurality ofaccess points 200, may transmit the removal request to the radio basestation 100. In this case, the removal request may include a list ofidentifiers of the access points 200 (an BSS ID list, and an EDD IDlist, for example). Further, in the second embodiment, the request forthe connection determination may be transmitted, via the AC, to theradio base station 100. Further, the response to the request for theconnection determination may be transmitted, via the AC, to the accesspoint 200.

In the above-described first embodiment, the access point 200 maytransmit the removal request to the radio base station 100, withoutusing, as the trigger, the connection request from the radio terminal10. For example, when the access point 200 does not desire the switchingprocess, by the radio terminal 10, from the mobile communication networkto the wireless LAN (when the load of the access point 200 alreadyexceeds the threshold value, for example), the removal request may betransmitted to the radio base station 100. The access point 200 maytransmit, by using, as the trigger, the determination that the switchingprocess is not desired, the removal request to the radio base station100.

In the above-described second embodiment, the response to the connectionrequest includes the connection refusal reason of the radio base station100; however, when the access point 200 does not receive the connectionrefusal reason from the radio base station 100 (when the access point200 independently makes the determination without requesting theconnection determination to the radio base station 100, for example),the response to the connection request may include the connectionrefusal reason in the access point 200.

In the above-described second embodiment, within the first coverage area100 of the cell managed by the radio base station 100, there is theaccess point 200; however, this is not limiting. When the first coveragearea 100A and the second coverage area 200A overlap partially, the radioterminal 10, the radio base station 100, and the access point 200 mayperform the operation according to the second embodiment.

In the above-described second embodiment, the radio base station 100 maypreviously transmit, before receiving the request for the connectiondetermination, the information indicating the connection refusal to theaccess point 200. For example, when knowing the transmission stop timeof the access point 200, the radio base station 100 is capable ofpreventing an increase in signaling by previously transmitting theinformation indicating the connection refusal to the access point 200.

In the above-described second embodiment, the radio base station 100 mayexclude (delete), when refusing the connection by the radio terminal 10to the access point 200 (that is, the response to the request for theconnection determination includes information indicating a connectionrefusal reason), the identifier of the access point 200 from the WLANIDlist. In this case, the radio base station 100 may transmit, by the SIB,the WLANID list in which the identifier of the access point 200 isremoved, to the radio terminal 10 within a cell of the radio basestation 100 (see first embodiment).

Although not particularly mentioned in the embodiments, a program may beprovided to cause a computer to execute each process performed by anyone of the radio terminal 10, the radio base station 100, and the accesspoint 200. Further, the program may be recorded on a computer-readablemedium. By using the computer-readable medium, it is possible to installthe program in a computer. Here, the computer-readable medium recordingthe program thereon may include a non-transitory recording medium. Thenon-transitory recording medium is not particularly limited; thenon-transitory recording medium may include a recording medium such as aCD-ROM or a DVD-ROM, for example.

Alternatively, a chip may be provided which is configured by: a memorythat stores therein a program for executing each process performed byany one of the radio terminal 10, the radio base station 100, and theaccess point 200; and a processor for executing the program stored inthe memory.

In each embodiment, the LTE is exemplified as the mobile communicationnetwork. However, the embodiment is not limited thereto. It may sufficewhen the mobile communication network is a network provided by acommunication carrier. Therefore, the mobile communication network maybe a UMTS (Universal Mobile Telecommunication System) or may be GSM(registered trademark).

1. A base station, comprising: a controller including a memory, whereinthe controller is configured to store a list in the memory, the listincluding at least one identifier of a Wireless Local Area Network(WLAN) access point, the controller is further configured to execute aprocess of receiving first information from a node configured to connectto the at least one WLAN access point, and the first informationincludes at least one identifier of a WLAN access point to be deletedfrom the list, and the controller is further configured to update thelist on a basis of the first information.
 2. The base station accordingto claim 1, wherein the controller is configured to execute a process oftransmitting a list based on the updated list.
 3. The base stationaccording to claim 1, wherein the controller is configured to execute aprocess of sending a response to the received first information, to thenode.
 4. The base station according to claim 1, wherein the controlleris configured to execute a process of sending a response to the receivedfirst information, to the node if the controller refuses updating thelist based on the first information, and the response indicates that thecontroller refuse to update the list based on the first information. 5.The base station according to claim 1, wherein the controller isconfigured to execute a process of receiving second information, and thesecond information includes at least one identifier of a WLAN accesspoint to be added to the list.
 6. An apparatus for a base station,comprising: a processor and a memory, the processor configured to causethe base station to: store a list in the memory, the list including atleast one identifier of a Wireless Local Area Network (WLAN) accesspoint, and receive first information from a node configured to connectto the at least one WLAN access point, wherein the first informationincludes at least one identifier of a WLAN access point to be deletedfrom the list, and the processor is further configured to cause the basestation to update the list on a basis of the first information.